This invention relates to a process for the continuous liquefaction of solid cellulosic biomass materials or lignite.
Alkaline materials such as sodium carbonate are known to catalyze the conversion of cellulosic materials into oil in the presence of carbon monoxide and water. This was discovered by Fischer and Schrader in 1921 and later confirmed by Appell, et al. in a series of laboratory and bench-scale experiments carried out at the Pittsburgh Energy Research Center of the Bureau of Mines, U.S. Department of the Interior, during the late 1960's to the early 1970's.
After the technical and economic feasibility was established, a pilot plant capable of treating up to 3 tons/day of wood chips was designed and constructed under the sponsorship of the U.S. Government. The process employed in the U.S. pilot plant comprises the following steps:
(1) An optional pretreatment of wood chips with water at 500.degree. F. (260.degree. C.) and 750 psig; PA1 (2) Drying and grinding of untreated or treated wood chips to less than about 4% by weight moisture and about -50 mesh average particle size; PA1 (3) Blending the wood particles with recycle product oil to form from about 30 to about 50% by weight of a wood in oil slurry at about 200.degree. F. (93.degree. C.); PA1 (4) Pumping the wood-oil slurry to develop up to 4,100 psig pressure; PA1 (5) Addition of carbon monoxide and aqueous sodium carbonate solution to the high pressure wood-oil slurry; PA1 (6) Heating the wood-oil-carbon monoxide-sodium carbonate-water mixture to up to about 750.degree. F. (400.degree. C.) temperature in a scraper blade preheater; PA1 (7) Conversion of wood to oil in a stirred tank reactor in which the wood-oil slurry is maintained at about 750.degree. F. (400.degree. C.); PA1 (8) Cooling the high pressure crude reaction product to less than 400.degree. F. (204.degree. C.) temperature; PA1 (9) Flashing the cooled, crude reaction product to a near atmospheric pressure to separate the dissolved gases; PA1 (10) Separation of water and solids from the crude oil product by a centrifuge; and PA1 (11) Recycling a portion of the product oil to prepare further wood-oil slurry.
The operation of the pilot plant during early 1976 to mid 1978 revealed certain operational and/or mechanical deficiencies. The product oil tended to polymerize, which resulted in difficulty of recycling the product oil as feed carrier oil. The scraper blade feed slurry heater and the agitated reactor experienced frequent failures. Difficulty was also encountered in attempts to separate water and solids from the crude oil product.
It is an object of this invention to provide a novel, improved process for the continuous conversion of solid biomass material into oil by treatment with carbon monoxide and water at elevated temperature and pressure in the presence of a catalyst and recycled product oil.
Another object of this invention is to provide a novel process for generating and supplying carbon monoxide for the reaction.
A further object of this invention is to provide a thermally efficient process for heating the reaction mixture to a desired temperature for carrying out the reaction.
Yet another object of this invention is to provide an improved process for the separation of water and solids from the crude product oil.
Still another object of this invention is to provide a novel, inexpensive process for recovering the catalyst from the crude product oil and recycling the catalyst for reuse in the biomass liquefaction.